During the end phase of the production of the cylinder liner or the cylinder which is integrated into the block of an internal combustion engine, the inner running face is subjected to what is known as honing or burnishing, to be precise with the aim of achieving such properties as the appropriate coefficient of roughness and thus to make correct functioning possible during many operating hours with high performance and a low combustion quantity of the lubricating oil.
During the honing or burnishing, a certain amount of folded metal accrues on the treated surface, which is disadvantageous, since it can lead to spalling of the coating which is applied to the outer running face of the piston ring, in particular if it is a ceramic coating which is applied with the aid of the PVD method (physical vapor deposition). If the spalling of the coating reaches a certain proportion, this leads to a reduction in the service life of the internal combustion engine, since the ring begins to wear through its support material, which also leads to damage of the combustion chamber seal.
One solution to increase the durability of the coatings on engine components (engine block or liners, fixed or removable), provided with at least one cylinder and consisting substantially of iron, is specified in document PI 1100176-3 by the same applicant, in which document the components are provided with a coating which is divided into three different layers which are applied on a metal substrate, wherein a first layer consists of pure silicon which is applied on the substrate and has the function of forming an interface with satisfactory adhesion between the metal substrate and the following layers which contain amorphous carbon, a transition layer contains components of silicon and amorphous carbon (a-C:H:Si), and finally a second layer on the working face consists of a pure composition of amorphous carbon (a-C:H), said coating being produced via the hollow cathode effect (HCE) by means of plasma-enhanced chemical vapor deposition (PECVD).
One alternative consists in using cylinder liners/cylinders with a thermospray coating, but this type of coating requires very much higher implementation costs, also on account of the greater layer thickness of the material which is used. In addition, this type of coating is not possible without a study which also incorporates the coating type of the piston rings with regard to the maximization of the results regarding the durability.
German patent document DE 102007008604 relates to a method for assessing honed structures, such as the running face of a liner/a cylinder, which makes it possible to quantify the proportion of folded metal, it being possible for the existing proportion to be examined and to be related to the spalling of the coating on the piston rings, and also other properties which it is desired to examine and which are linked thereto.
German patent document DE 10302055 relates to a white light interferometer which makes it possible, under the influence of an optical or magnetic field, to perform the in-depth scanning of an object, with the result that the presence and the proportions of folded metal on the inner running face of a liner/a cylinder can be determined.
Finally, German patent document DE 102005023212 relates to a method for increasing the measuring speed and measuring accuracy, which method makes more accurate measuring of the objects possible.
The presence of this type of measuring technology has made it possible for the applicant to very accurately examine the percentage quantification of the proportion of folded metal in burnished structures; it was possible to examine the existing proportion and to relate it to the spalling of the coating on the piston rings, and also other properties which the applicant desired to examine and which are linked thereto, to be precise with the aid of parameters in conjunction with the product development, such as performance, durability and costs.